Three GPI-anchored alkaline phosphatases are involved in the intoxication of Cry1Ca toxin to Spodoptera exigua larvae

[Display omitted] •Five SeALPs are highly expressed in Spodoptera exigua larval gut.•Ingestion of dsRNAs targeting five SeALPs significantly reduced corresponding gene expression.•Ingestion of SeALP1, SeALP2 and SeALP4 dsRNAs decreased Cry1Ca-induced larval mortality.•SeALP1, SeALP2 and SeALP4 are i...

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Published in:Journal of invertebrate pathology 2018-01, Vol.151, p.32-40
Main Authors: Ren, Xiang-Liang, Hu, Hong-Yan, Jiang, Wei-Li, Ma, Xiao-Yan, Ma, Ya-Jie, Li, Guo-Qing, Ma, Yan
Format: Article
Language:English
Subjects:
Alkaline phosphatase
Bacillus thuringiensis
Crystal toxin
RNA interference
S. exigua
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Summary:[Display omitted] •Five SeALPs are highly expressed in Spodoptera exigua larval gut.•Ingestion of dsRNAs targeting five SeALPs significantly reduced corresponding gene expression.•Ingestion of SeALP1, SeALP2 and SeALP4 dsRNAs decreased Cry1Ca-induced larval mortality.•SeALP1, SeALP2 and SeALP4 are involved in the intoxication of Cry1Ca to S. exigua. Glycosylphosphatidylinositol (GPI)-anchored alkaline phosphatase (ALP) isoforms are crucial for the intoxication of crystal proteins (Cry) to several insect species. We cloned five SeALPs from the larval midgut of Spodoptera exigua, a major pest of many crops. All five SeALPs contain a signal peptide at the N-terminus, a phosphatase domain, and a GPI-anchor site at the C-terminus. Additionally, the sequences encode two or three potential N-glycosylation sites. The five SeALPs were highly expressed at the larval stage, especially in the larval gut or Malpighian tubules. Ingestion over four consecutive days of double-stranded RNAs (dsRNAs) targeting SeALP1, SeALP2, SeALP3, SeALP4, and SeALP5 significantly reduced the corresponding mRNA levels by 60.0%, 40.0%, 65.6%, 48.1%, and 69.1% respectively, compared with the levels in control larvae that fed on non-specific dsRNA (dsEGFP). When larvae that previously ingested phosphate buffered saline (PBS)-, dsEGFP-, or five dsSeALPs-overlaid diets were then exposed to a diet containing Cry1Ca, the larval mortalities after six days were 70.0%, 71.8%, 49.1%, 54.9%, 65.3%, 52.5%, and 77.4%, respectively. ANOVA analysis revealed that the larvae that previously fed on the dsSeALP1-, dsSeALP2-, and dsSeALP4-overlaid diets had significantly lower mortalities than those that previously ingested the PBS-, dsEGFP-, dsSeALP3- and dsSeALP5-overlaid diets. The results suggest that SeALP1, SeALP2 and SeALP4 are involved in the intoxication of Cry1Ca to S. exigua larvae.
ISSN:0022-2011
1096-0805
DOI:10.1016/j.jip.2017.10.009